Human immunodeficiency virus (HIV) is the etiological agent of acquired immunodeficiency syndrome (AIDS). AIDS is characterized by CD4+ T lymphocyte depletion. Tat, the viral trans-activator encoded by the HIV-1 genome, is responsible for HIV-1 replication at the transcriptional level in HIV-1 infected cells by binding the trans-activation response region (TAR) and recruiting cdk9/cyclin T1, p300/CBP, SWI/SNF, and RNA Polymerase II. Sustained HIV-1 replication further progresses infected T cells towards AIDS. The long-term goal of our research is to understand how the chromatin environment, Tat, and chromatin remodelers/modifiers cooperate to influence HIV-1 transcription. Tat, in its unmodified form, associates with the histone acetyltransfersase p300/CBP. However, we have recently found that acetylated Tat binds BRG1, a component of the SWI/SNF chromatin remodeling complex. A further test of which SWI/SNF complex is involved in activated transcription points to specific use of PBAF complex. This Tat-SWI/SNF complex is sufficient to remove/remodel nuc-1 from the HIV-1 promoter to allow for TAR-specific HIV-1 transcription. We also show that BRG1 and Baf200 play critical role in HIV-1 replication. Therefore, these results led us to speculate that Tat-SWI/SNF plays a role Tat activated HIV-1 transcription. Our hypothesis is that unmodified Tat complexes with p300/CBP and cdk9/cyclin T1 to initiate HIV-1 transcription while acetylated Tat complexes with SWI/SNF and p300/CBP- associated factor (p/CAF) to promote transcriptional elongation. However, p300/CBP may also be involved in Tat-mediated transcriptional elongation. Our rationale for these studies is based on mounting data demonstrating that the chromatin environment and chromatin-associated factors are critical in regulating HIV-1 expression. Hence, there is now added emphasis on identifying chromatin factors/modifications that aid in transition through the inhibitory chromatin complex. . The following specific aims address our hypothesis: (I) What is the significance of the Tat-p300/CBP and Tat-p/CAF complexes in chromatin marking and transcription elongation on the HIV-1 promoter and open reading frames in cell lines and PBMC infected cells? (II) What is the role of the Tat- SWI/SNF (Tat-PBAF) complex in chromatin remodeling at the HIV-1 LTR in infected cell lines and PBMC infected cells? Data obtained from these studies will shed light on how the chromatin environment regulates Tat activated HIV-1 transcription. PUBLIC HEALTH RELEVANCE: Narrative Human immunodeficiency virus (HIV) is the causative agent of acquired immunodeficiency syndrome (AIDS). A viral protein encoded by the HIV-1 genome (Tat), is responsible for HIV-1 replication at the level of DNA. Our research seeks to understand how the proteins and factors (chromatin) present on HIV-1 DNA influence viral expression when acting through the actions of Tat. Based on the mounting data demonstrating that the chromatin environment is critical in regulating HIV-1 expression, there is now an added emphasis on chromatin-associated proteins as novel therapeutic targets. This work will shed new light on the role of chromatin in Tat-mediated HIV-1 expression.